Show or hide a toolbar

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=false and destructiveHint=true, so the mutation profile is covered. The description adds real context beyond that: it names CustomizableUI.setToolbarVisibility and states the change 'applies immediately,' telling the agent there is no restart or deferred commit — though it omits whether visibility persists across sessions or how to revert.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two dense sentences: the capability first, then the disambiguation. Every clause carries information and nothing is padded.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-parameter toggling tool with full schema coverage, annotations, and no output schema, this is nearly sufficient. The one gap is not mentioning the menubar-specific sibling it overlaps with, which could produce a suboptimal tool choice.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, with both parameters documented including example ids, so the baseline is 3. The description's examples of toolbars loosely map to the 'toolbar' parameter but add no id syntax or accepted-value detail beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (show or hide) and resource (a whole toolbar), gives concrete examples (bookmarks toolbar, menu bar), and explicitly contrasts scope with browser_set_toolbar_widget. An agent can identify the tool without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It names the alternative and the condition that selects it: this tool is 'coarser than browser_set_toolbar_widget, which moves individual widgets.' However, the description cites 'the menu bar' as a use case while a dedicated sibling browser_set_menubar_visibility exists, and it never routes the agent to that more specific tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.